Fix Visual Studio 2015 Razor Editor Blow Up

Visual Studio 2015 has been RTM for one month. However, it blows up very often, such as Razor editor. When I try to open any .cshtml file, it blows up with this error, then the syntax highlight is gone. I tried to uninstall all add-on, even repair install VS2015 can't get it working.

The detailed error message is:

System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.ArgumentException: Item has already been added. Key in dictionary: 'RazorSupportedRuntimeVersion'